1. Field of the Invention
The present invention relates to a combined isolating switch-circuit breaker for on-load breaking and isolation of an electric circuit which, generally, will have to be with visible contact opening.
2. Description of the Prior Art
Generally, it is known that the isolation of an electric installation must guarantee total isolation thereof from the power supply source. Therefore, standardization prohibits the use of switches (which make the current and break it on load) as isolating switch members, even if the break is visible. This prohibition is due to the fact that the material opening of a contact circuit for breaking the current does not guard against the loss of insulation due to pollution of the insulators of the contact circuit by the electric arc which occurs at the moment of breaking.
Thus, any installation must associate with the circuit breaker (manual or automatic) a specific device ensuring the isolating function such for example an isolating switch, an isolating fuse holder, isolating terminals, etc. . .
This addition of an isolating switch therefore increases the complexity of the installation and increases its cost.
The purpose of the invention is therefore more particularly to associate in the same apparatus the circuit breaking and isolating functions.
A combined isolating switch-circuit breaker has already been proposed to this end of the type comprising at least one fixed contact breaker element, one fixed isolating contact element, at least one mobile assembly comprising a mobile breaking contact element connected electrically to a mobile isolating contact element, these two mobile contact elements being adapted for cooperating respectively with the two fixed contact elements and means for moving the mobile assembly between an open position in which the fixed contact elements are separated from the mobile contact elements and a closed position in which the fixed contact elements are in electrical contact with the corresponding mobile contact elements. In such a combined isolating switch-contact breaker, the arrangement of the mobile contact elements with respect to the fixed contact elements as well as the nature of the movements of the mobile assembly are adapted so that, when passing from the open to the closed position, the fixed isolating contact element is electrically connected to the mobile isolating contact element before the electric contact is established between the fixed breaking element and the mobile contact breaking element and, conversely, when passing from the closed to the open position, the fixed breaking contact element is separated from the mobile contact breaking element before disconnection of the fixed isolating contact element and the mobile isolating contact element.
However, in this type of combined device, so that the isolating function is not polluted by the breaking arc, it is necessary to provide appropriate arrangements so that the travel of the mobile assembly between the point where the fixed and mobile contact breaking elements separate mechanically and the point where the isolating contact elements separate mechanically is as large as possible.
Such an arrangement in fact guarantees that, on opening of the isolating contacts, the combined device does not have the current flowing therethrough.
In practice, however, this solution has a number of drawbacks. It involves more especially, in order to obtain a sufficiently long opening travel path, with, in addition, good insulating properties between the breaking and isolating contacts:
combined devices having a relatively space consuming structure; PA0 the use of relatively complex kinematic drive chain (because of the length of the travel path).
The aim of the invention is therefore to overcome these drawbacks. For this, it provides an arrangement for significantly reducing the travel path of the mobile assembly without for all that increasing the risk of pollution of the isolating contacts, so as to make it possible to construct combined devices of reduced size and so less costly and less space consuming, which may be actuated by simple drive mechanisms.